Characterization and antitumor activity of the extracellular carbohydrate polymer from the cyanobacterium Synechocystis ΔsigF mutant

Cyanobacterial extracellular carbohydrate polymers are particularly attractive for biotechnological applications. Previously, we determined the monosaccharidic composition of the polymer of a Synechocystis ΔsigF overproducing mutant. Here, we further characterized this polymer, demonstrated that it is possible to recover it in high yields, and successfully use it for biomedical research. This amorphous polymer is formed by a mesh of fibrils/lamellar structures with high porosity, is constituted by high molecular mass fractions, is highly sulfated and displays low viscosity, even in highly concentrated aqueous solutions. FTIR analysis confirmed the presence of several functional groups. We demonstrated that the ΔsigF polymer has strong biological activity, decreasing the viability of melanoma, thyroid and ovary carcinoma cells by inducing high levels of apoptosis, through p53 and caspase-3 activation. Therefore, the ΔsigF Synechocystis mutant is a promising platform for the sustainable production of biological active carbohydrate polymer(s) with the desired characteristics for biomedical applications. •The Synechocystis ΔsigF polymer (SP) yield is 4-fold higher than wild-type.•SP is formed by fibrils/lamellae with high porosity and molecular mass fractions.•SP is sulphated, has several functional groups and non-Newtonian fluid behaviour.•SP strongly reduces the viability of different human tumor cell lines.•SP induces apoptosis in the human melanoma cell line Mewo via p53 and caspase-3.